The act of vigorously whipping your dickback and forth (left and right) so that it makes contact with your legs. The resulting impact produces a smacking sound, and if done rapidly, it can sound like clapping.
Instead of clapping with his hands at the end of the show, George stood up, dropped his pants, and started penis clapping like a boss.
when two nude men stand facing one another and thrust their pelvises causing their penises to fly forward making contact and emitting a percussive sound.
somebody who has nothing better to do than to go home, lay on his bed, bored, and flap his penis around with his two hands continuously because he has no friends, or anything to do.
"dude do you think that moonster kid has any friends"
"who nathan? are you fucking serious man? hes such a dick, of course not, he probably just goes home every night and flaps his penis around out of boredom"
"what do you expect, hes a fucking dick, thats what he gets, and have you seen his clothes?"
"or his hair? i mean its like he WANTS to be a penisflapper..."